Many storage systems adopt a so-called RAID (Redundant Arrays of Inexpensive/Independent Disks) technique to enhance the availability of the system. A RAID technique is a technique for computing parity or other redundant data from the write data received from a superior device such as a host computer, and storing the write data and the parity in a dispersed manner to different storage devices. By adopting the RAID technique, even when failure occurs to a portion of the storage devices and data cannot be read from those storage devices, the information stored in the other storage devices can be used to regenerate data.
In the RAID technique, the load of the process performed by the controller (storage controller) installed in the storage system or the amount of data transferred between components within the storage system (such as between the storage controller and the storage device) is increased in order to compute the parity. Various techniques have been devised in the prior art to suppress the increase of processing loads and the amount of data transfer. For example, Patent Literature 1 teaches a storage system having the function for generating parity and the like provided to the storage device side to suppress the amount of data transfer that occurs between the storage controller and the storage device.